Process of treating lead-zinc sulphide ores



NIELS C. CHRISTENSEN, 03F SALT LE CITY,

PBOCESS'OF TREATING LEAD-ZINC SULPHTDE GEES.

No Drawing. Original application filed October 11, 1919, Serial No. 330,035. Divided and thia application filed April 9, 1920. Serial No. 372,692.

T 0 all w ltom it may concern Be it known that I, NIELs C. CHRISTENSEN,

a citizen of the United States, residing at Salt Lake City in the county of Salt Lake and State of {Italy have invented certain new and useful Processes of Treating Lead- Zinc sulphide Ores, of which the followingr is a specification. g

his invention relates to the treatment of lead zinc-sulphide ores. My process is a combination of the rocess of treating zinc sulphide ores descri ed in my application Serial No. 327,402 and the processes for treating galena ores described in my applications Serial Nos. 327,400 and 327,401.

The process consists in treating the comminuted ore or concentrates with a hot concentrated sulphuric acid solution of such strength that the zinc is dissolved as the sulphate and the sulphur driven ofi' as H S, v I

'l'he'hot solution containing the lead and.

as indicated in the following equation:

ZnS+H,SO,:ZnSO,l-H,S.

This operation should preferably be carried out with acid of a concentration between 50% and 70% ll-LSO in order to avoid sulphating the galena or dissolving any of the lead as a sulphate in the hot acid. If acid stronger than 70% H SQ, is used the galena is somewhat acted upon and thelead sulphate formed is dissolved in the hot acid and contaminates the zinc sulphate. The silver sulphide in the blends and gale-na is not acted upon by the 50%70% H 80, but stronger acid does act upon the silver and sulphates it in about the same proportion as the lead is dissolved. By using approximately acid at a temperature near its boiling point practically all the zinc is dissolved as a sulphate, and the galena and silver sulphide are not sulphated nor dissolved. As noted in my application Ser. No. 327,402, the hot acid Will hold much more .ZnSO, in solution than the cold acid, and I take advantage of this to separate the zinc sulphate from the solution. Such a proportion of acid to ore is used that a hot concentrated solution of zinc sulphate is formed by the foregoing treatment. This hot acid solution of zinc sulphate is filtered away from the residue of the ore and cooled, and the zinc sulphate precipitated and the cold acid filtered or drained away, leaving the zinc sulphate. By this method practically all the zinc may be separated from the sulphide ores of zinc as a high grade zlnc sulphate product, leaving the galena and silver untouched along with the pyrite, chalcopyrite and gangue minerals.

The se aration of the lead and silver from this resl ue from the zinc treatment is made by treating it with a hot chloride solution v chloride.

silver is filtered away from the gangue material and the-silver is preferably precipitated therefrom with metallic lead and the lead either by cooling or by electrolysis, or

by a combination of both. The hot chloride I solutions dissolve a much larger amount of lead chloride than the cold solutions, and the lead chloride may be separated from the chloride solution by taking advantage of this fact. Such a proportion of solution to ore is used that a hot concentrated solution of lead chloride is secured by the before described treatment. This solution is filtered aWay from the oreand then cooled and the lead chloride precipitated and separated from the cold solution. The precipitation of the lead by electrolysis is preferably used when the dissolving solution contains ferric chloride and the ferrous chloride thus formed is regenerated by the chlorine given off in the electrolysis. The chloride solution may be electrolyzed with an insoluble anode in a cell with a diaphragm separating the cell into anode and cathode compartments. The ferrous solution containing the lead chloride is led first into the cathode compartment where the lead is precipitated, and then into the anode compartment where the ferrous chloride is changed to ferric chloride by the chlorine as indicated below:

The precepitated lead chloride may also be melted and electrolyzed to secure lead bullion and chlorine. The chlorine thus secured is led into the ferrous solution where it unites with the ferrous chloride to form ferric chloride thus regenerating the dissolvin solution.

y this process practically all the lead and all the silver in the galena and blende (or in the ore in the form of sulphide) are re= covered in a very pure condition.

The residue from this treatment is especially well suited to treatment by flotation to separate the pyrite or chalcopyrite from the silicious gangue material and a very complete recovery of these may be made by this method From the foregoing it is seen that by my combined process a practically complete separation and practically complete extraction of the lead, zinc, silver, and pyrite and chalcopyrite, may be secured from the complex lead-zinc sulphide ores which have long been an unsolved metallurgical problem.

This application is a division of my application Serial No. 330,035 filed on or about October 11, 1919.

Having described my process what I claim and desire to patent is: Y

1. The process of treating lead-zinc sulphide ores and concentrates which consists in treating the comminuted ore with hot concentrated sulphuric acid, thereby dissolving the zinc as a sulphate, without dissolving any substantial portion of the lead, separating the hot acid solution from the residue of the ore, and cooling said solution, and thereby precipitating zinc sulphate therefrom, treating the residue of ore from foregoing treatment with a hot concentrated chloride solution containing ferric chloride, and thereby dissolving the lead and silver as chlorides and reducing the ferric iron to the ferrous condition, and separating last said solution from the remainder of the ore. and precipitating the silver therefrom and precipitating the lead from the lead chloride thus formed by electrolysis and using the chlorine thus formed to change the ferrous iron formed by above said treatment to the ferric condition, and using said ferric solution in the treatment of more ore.

2. The process of treating lead-zinc sulphide ores and concentrates which consists in treating the comminuted ore with hot concentrated sulphuric acid, thereby dissolving the zinc as a sulphate without dissolving any substantial portion of the lead, separating the hot acid solution from the residue of the ore, and cooling said solution, and thereby precipitating zinc sulphate therefrom, treating the residue of ore from foregoing treatment with a hot concentrated ohloride'solution containing ferric chloride, and thereby dissolving the lead and silver as chlorides and reducing the ferric iron to the ferrous condition, and separating last said solution from the remainder of the ore, and

ments by flotation for the recovery of the remaining sulphides therefrom.

3. The process of treating lead-zinc sulphide ores and concentrates which consists in treating the comminuted ore with hot concentrated sulphuric acid containing between 50% and acid, thereby dissolving the zinc as a sulphate, separating the hot acid solution from the residue of the ore, and cooling said solution, and thereby precipitating zinc sulphate therefrom, treating the residue of ore from the foregoing treatment with a hot concentrated chloride solution containing ferric chloride, and thereby dissolving the lead and silver as chlorides and reducing the ferric iron to the ferrous condition, and separating last said solution from the remainder of the ore, and precipitating the silver therefrom and precipitating the lead from the lead chloride thus formed by electrolysis and using the chlorine thus formed to change the ferrous iron formed by above said treatment to the ferric condition, and using said ferric solution in the treatment of more ore.

4. The process of treating lead-zinc sulphide ores and concentrates which consists in treating the comminuted-ore with hot concentrated sulphuric acid containing'between 50% and 75% acid, thereby dissolving the zinc as a sulphate, separating the hot acid solution from the residue of the ore, and cooling said solution and thereby precipitating zinc sulphate therefrom, treating the residue of ore from foregoing treatment with a hot concentrated chloride solution containing ferric chloride, and thereby dissolving the lead and silver as chlorides and reducing the ferric iron to the ferrous condition, and separating last said solution from the remainder of the ore, and precipitating the silver therefrom and precipitating the lead from the lead chloride thus formed by electrolysis and using the chlorine thus formed to change the ferrous iron formed bv above said treatment to the ferric condition, and using said ferric solution in the treatment of more ore, and treating the residue from-before mentioned treatments by flotation for the recovery of the remaining 125 sulphides therefrom.

In testimony whereof I have signed my name to this specification.

NIELS c. CHRISTENSEN. 

